<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <meta name="viewport"
          content="width=device-width, initial-scale=1.0, minimum-scale=1.0, maximum-scale=1.0, user-scalable=no">
    <link rel="stylesheet" href="css/index.css">
    <style>
        .div{
            position: absolute;
            top: -150px;
            left: -180px;
            box-sizing: border-box;
            font-size: 0;
        }
        .a{
            width: 280px;
            height: 20px;
            border: 1px solid red;
            box-sizing: border-box;
            float: left;
        }
    </style>

</head>
<body>
<div class="div" style="width: 600px;height: 500px;border: 1px solid #000; transform: scale(.6);">
    <div class="a" style="margin-right: 38px"></div>
    <div class="a"></div>
</div>
<script>
    console.info(document.getElementsByClassName('div')[0].offsetTop )
</script>
</body>
